IPv6 Firewall: Penggunaan

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Cek untuk Dukungan

Load module, jika sudah di compil

# modprobe ip6_tables 

Cek untuk kemampuan

# [ ! -f /proc/net/ip6_tables_names ] && echo "Current kernel doesn't support 'ip6tables' firewalling (IPv6)!" 

Belajar Mengunakan ip6tables

Lihat Semua Entri IPv6 netfilter

Pendek

# ip6tables -L 

Panjang

# ip6tables -n -v --line-numbers -L 

Lihat filter tertentu

# ip6tables -n -v --line-numbers -L INPUT 

Masukan aturan log rule pada input filter dengan opsi tertentu

# ip6tables --table filter --append INPUT  -j LOG --log-prefix "INPUT:" --log-level 7 

Masukan aturan drop pada input filter

# ip6tables --table filter --append INPUT  -j DROP 

Buang aturan berdasarkan nomor

# ip6tables --table filter --delete INPUT 1 

Aktifkan connection tracking

Sejak kernel versi 2.6.20 IPv6 connection tracking sudah didukung dengan baik dan sebaiknya digunakan daripada menggunakan rules filter stateless

# ip6tables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

Ijinkan ICMPv6

Menggunakan kernel lama (kernel 2.4.5 tidak di patch dan iptables-1.2.2) kita tidak dapat menspesifikasi tipe

Terima ICMPv6 yang masuk melalui tunnel

# ip6tables -A INPUT -i sit+ -p icmpv6 -j ACCEPT 

Terima ICMPv6 yang keluar melalui tunnel

# ip6tables -A OUTPUT -o sit+ -p icmpv6 -j ACCEPT 

Kernel baru memungkinkan untuk mengijinkan tipe ICMPv6:

# ip6tables -A INPUT -p icmpv6 --icmpv6-type echo-request -j ACCEPT

Rate-limiting

Karena kemungkinan bisa saja terjadi badai ICMPv6, kita perlu menggunakan rate limiting paling tidak untuk ICMPv6. Selain itu, kita perlu menambahkan rule rate limiting untuk logging supaya tidak ada serangan DoS terhadap syslog maupun partisi log. Contoh dari rate limiting ICMPv6 adalah sebagai berikut:

# ip6tables -A INPUT --protocol icmpv6 --icmpv6-type echo-request
¬ -j ACCEPT --match limit --limit 30/minute

Ijinkan SSH yang masuk

Berikut adalah contoh rule yang mengijinkan sambungan masuk SSH dari address IPv6 tertentu.

Ijin SSH masuk dari 2001:0db8:100::1/128

# ip6tables -A INPUT -i sit+ -p tcp -s 2001:0db8:100::1/128 --sport 512:65535 --dport 22 -j ACCEPT 

Ijin responds paket (tidak di perlukan kalau connection tracking digunakan)

# ip6tables -A OUTPUT -o sit+ -p tcp -d 2001:0db8:100::1/128 --dport 512:65535 --sport 22 ! --syn -j ACCEPT

AKtifkan tunnel IPv6-in-IPv4

Untuk menerima paket tunnel IPv6-in-IPv4 , kita perlu menambahkan rule di firewall IPv4 terhadap paket tersebut, contoh

Menerima masukan IPv6-in-IPv4 di interface ppp0

# iptables -A INPUT -i ppp0 -p ipv6 -j ACCEPT 

Mengijinkan keluaran IPv6-in-IPv4 ke interface ppp0

# iptables -A OUTPUT -o ppp0 -p ipv6 -j ACCEPT 

Jika kita hanya mempunyai statik tunnel, kita dapat menentukan address IPv4 tersebut, seperti,

Menerima masukan IPv6-in-IPv4 di interface ppp0 dari tunnel endpoint 192.0.2.2

# iptables -A INPUT -i ppp0 -p ipv6 -s 192.0.2.2 -j ACCEPT 

Mengijinkan keluaran IPv6-in-IPv4 di interface ppp0 dari tunnel endpoint 1.2.3.4

# iptables -A OUTPUT -o ppp0 -p ipv6 -d 192.0.2.2 -j ACCEPT

Proteksi terhadap permohonan sambungan masuk TCP

VERY RECOMMENDED! For security issues you should really insert a rule which blocks incoming TCP connection requests. Adapt "-i" option, if other interface names are in use!

Block incoming TCP connection requests to this host

# ip6tables -I INPUT -i sit+ -p tcp --syn -j DROP 

Block incoming TCP connection requests to hosts behind this router

# ip6tables -I FORWARD -i sit+ -p tcp --syn -j DROP 

Perhaps the rules have to be placed below others, but that is work you have to think about it. Best way is to create a script and execute rules in a specified way.

Proteksi terhadap sambungan masuk UDP

ALSO RECOMMENDED! Like mentioned on my firewall information it's possible to control the ports on outgoing UDP/TCP sessions. So if all of your local IPv6 systems are using local ports e.g. from 32768 to 60999 you are able to filter UDP connections also (until connection tracking works) like:

Block incoming UDP packets which cannot be responses of outgoing requests of this host

# ip6tables -I INPUT -i sit+ -p udp ! --dport 32768:60999 -j DROP 

Block incoming UDP packets which cannot be responses of forwarded requests of hosts behind this router

# ip6tables -I FORWARD -i sit+ -p udp ! --dport 32768:60999 -j DROP 

Contoh

Simple example for Fedora

Following lines show a simple firewall configuration for Fedora 6 (since kernel version 2.6.20). It was modfied from the default one (generated by system-config-firewall) for supporting connection tracking and return the proper ICMPv6 code for rejects. Incoming SSH (port 22) connections are allowed.

File: /etc/sysconfig/ip6tables

*filter :INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:RH-Firewall-1-INPUT - [0:0]
-A INPUT -j RH-Firewall-1-INPUT
-A FORWARD -j RH-Firewall-1-INPUT
-A RH-Firewall-1-INPUT -i lo -j ACCEPT
-A RH-Firewall-1-INPUT -p icmpv6 -j ACCEPT
-A RH-Firewall-1-INPUT -p 50 -j ACCEPT
-A RH-Firewall-1-INPUT -p 51 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp --dport 5353 -d ff02::fb -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m udp --dport 631 -j ACCEPT 
-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state NEW -p tcp --dport 22 -j ACCEPT
-A RH-Firewall-1-INPUT -j REJECT --reject-with icmp6-adm-prohibited
COMMIT 

For completeness also the IPv4 configuration is shown here:

File: /etc/sysconfig/iptables

*filter :INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:RH-Firewall-1-INPUT - [0:0]
-A INPUT -j RH-Firewall-1-INPUT
-A FORWARD -j RH-Firewall-1-INPUT
-A RH-Firewall-1-INPUT -i lo -j ACCEPT
-A RH-Firewall-1-INPUT -p icmp --icmp-type any -j ACCEPT
-A RH-Firewall-1-INPUT -p 50 -j ACCEPT
-A RH-Firewall-1-INPUT -p 51 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp --dport 5353 -d 224.0.0.251 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m udp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
-A RH-Firewall-1-INPUT -j REJECT --reject-with icmp-host-prohibited
COMMIT 

Usage:

Create/modify the configuration files

Activate IPv4 & IPv6 firewalling

# service iptables start
# service ip6tables start

Enable automatic start after reboot

# chkconfig iptables on
# chkconfig ip6tables on

Contoh Yang Lebih Kompleks

Kalimat berkut menunjukan sebuah contoh yang lebih sophisticated tapi masih tetap filter stateless.

# ip6tables -n -v -L 
Chain INPUT (policy DROP 0 packets, 0 bytes) 
 pkts bytes target     prot opt in     out     source               destination
    0     0 extIN      all      sit+   *       ::/0                 ::/0 
    4   384 intIN      all      eth0   *       ::/0                 ::/0 
    0     0 ACCEPT     all      *      *       ::1/128              ::1/128 
    0     0 ACCEPT     all      lo     *       ::/0                 ::/0 
    0     0 LOG        all      *      *       ::/0                 ::/0       
¬        LOG flags 0 level 7 prefix `INPUT-default:' 
    0     0 DROP       all      *      *       ::/0                 ::/0 
 
Chain FORWARD (policy DROP 0 packets, 0 bytes) 
 pkts bytes target     prot opt in     out     source               destination
¬ 
    0     0 int2ext    all      eth0   sit+    ::/0                 ::/0 
    0     0 ext2int    all      sit+   eth0    ::/0                 ::/0 
    0     0 LOG        all      *      *       ::/0                 ::/0       
¬        LOG flags 0 level 7 prefix `FORWARD-default:' 
    0     0 DROP       all      *      *       ::/0                 ::/0 
 
Chain OUTPUT (policy DROP 0 packets, 0 bytes) 
 pkts bytes target     prot opt in     out     source               destination
¬ 
    0     0 extOUT     all      *      sit+    ::/0                 ::/0 
    4   384 intOUT     all      *      eth0    ::/0                 ::/0 
    0     0 ACCEPT     all      *      *       ::1/128              ::1/128 
    0     0 ACCEPT     all      *      lo      ::/0                 ::/0 
    0     0 LOG        all      *      *       ::/0                 ::/0       
¬        LOG flags 0 level 7 prefix `OUTPUT-default:' 
    0     0 DROP       all      *      *       ::/0                 ::/0 
 
Chain ext2int (1 references) 
 pkts bytes target     prot opt in     out     source               destination
¬ 
    0     0 ACCEPT     icmpv6    *      *       ::/0                 ::/0 
    0     0 ACCEPT     tcp      *      *       ::/0                 ::/0       
¬        tcp spts:1:65535 dpts:1024:65535 flags:!0x16/0x02 
    0     0 LOG        all      *      *       ::/0                 ::/0       
¬        LOG flags 0 level 7 prefix `ext2int-default:' 
    0     0 DROP       tcp      *      *       ::/0                 ::/0 
    0     0 DROP       udp      *      *       ::/0                 ::/0 
    0     0 DROP       all      *      *       ::/0                 ::/0 
 
Chain extIN (1 references) 
 pkts bytes target     prot opt in     out     source               destination
¬ 
    0     0 ACCEPT     tcp      *      *       3ffe:400:100::1/128  ::/0       
¬        tcp spts:512:65535 dpt:22 
    0     0 ACCEPT     tcp      *      *       3ffe:400:100::2/128  ::/0       
¬        tcp spts:512:65535 dpt:22 
    0     0 ACCEPT     icmpv6    *      *       ::/0                 ::/0 
    0     0 ACCEPT     tcp      *      *       ::/0                 ::/0       
¬        tcp spts:1:65535 dpts:1024:65535 flags:!0x16/0x02 
    0     0 ACCEPT     udp      *      *       ::/0                 ::/0       
¬        udp spts:1:65535 dpts:1024:65535 
    0     0 LOG        all      *      *       ::/0                 ::/0       
¬        limit: avg 5/min burst 5 LOG flags 0 level 7 prefix `extIN-default:' 
    0     0 DROP       all      *      *       ::/0                 ::/0 
 
Chain extOUT (1 references) 
 pkts bytes target     prot opt in     out     source               destination
¬  
    0     0 ACCEPT     tcp      *      *       ::/0                
¬ 2001:0db8:100::1/128tcp spt:22 dpts:512:65535 flags:!0x16/0x02 
    0     0 ACCEPT     tcp      *      *       ::/0                
¬ 2001:0db8:100::2/128tcp spt:22 dpts:512:65535 flags:!0x16/0x02 
    0     0 ACCEPT     icmpv6    *      *       ::/0                 ::/0 
    0     0 ACCEPT     tcp      *      *       ::/0                 ::/0       
¬        tcp spts:1024:65535 dpts:1:65535 
    0     0 ACCEPT     udp      *      *       ::/0                 ::/0       
¬        udp spts:1024:65535 dpts:1:65535 
    0     0 LOG        all      *      *       ::/0                 ::/0       
¬        LOG flags 0 level 7 prefix `extOUT-default:' 
    0     0 DROP       all      *      *       ::/0                 ::/0 
 
Chain int2ext (1 references) 
 pkts bytes target     prot opt in     out     source               destination
¬ 
    0     0 ACCEPT     icmpv6    *      *       ::/0                 ::/0 
    0     0 ACCEPT     tcp      *      *       ::/0                 ::/0       
¬        tcp spts:1024:65535 dpts:1:65535 
    0     0 LOG        all      *      *       ::/0                 ::/0       
¬        LOG flags 0 level 7 prefix `int2ext:' 
    0     0 DROP       all      *      *       ::/0                 ::/0 
    0     0 LOG        all      *      *       ::/0                 ::/0       
¬        LOG flags 0 level 7 prefix `int2ext-default:' 
    0     0 DROP       tcp      *      *       ::/0                 ::/0 
    0     0 DROP       udp      *      *       ::/0                 ::/0 
    0     0 DROP       all      *      *       ::/0                 ::/0 
 
Chain intIN (1 references) 
 pkts bytes target     prot opt in     out     source               destination
¬ 
    0     0 ACCEPT     all      *      *       ::/0                
¬ fe80::/ffc0:: 
    4   384 ACCEPT     all      *      *       ::/0                 ff02::/16 
 
Chain intOUT (1 references) 
 pkts bytes target     prot opt in     out     source               destination
¬ 
    0     0 ACCEPT     all      *      *       ::/0                
¬ fe80::/ffc0:: 
    4   384 ACCEPT     all      *      *       ::/0                 ff02::/16 
    0     0 LOG        all      *      *       ::/0                 ::/0       
¬        LOG flags 0 level 7 prefix `intOUT-default:' 
    0     0 DROP       all      *      *       ::/0                 ::/0